COMPARISON OF COTTON GENOTYPES VARYING IN CANOPY CHARACTERISTICS IN 76-CM VS 102-CM ROWS

Our previous findings with cotton (Gossypium hirsutum L.) indicated th at a leaf shape variant with reduced leaf area (okra-leaf) yielded mor e in 51-cm rows than in 102-cm rows. Yield of a normal-leaf type was u naffected, The objectives of this study were to determine whether this same response would occur with genotypes varying in canopy characteri stics when grown in rows spaced 76 and 102 cm. From 1991 to 1993, seve n to 14 genotypes (including two okra-leaf and one ultra-short season type) were grown in the field in 76- and 102-cm row spacings. The 1991 part of the study encompassed lour soil types and the 1992 and 1993 s tudy was grown on a Bosket fine sandy loam. Irrigation was provided wh en necessary to minimize water stress. The percentage of photosyntheti c photon Bur density (PPFD) intercepted and yield were determined. The 76-cm row spacing intercepted significantly more PPFD than 102-cm row s up until 80 d after planting. Row spacing did not affect yield in ei ther an excellent environment (1991, 1475 kg ha(-1)) or in a stressed environment (1993, 905 kg ha(-1)). However, 76-cm rows outyielded 102- cm rows by 15% in 1992 (1280 vs. 1100 kg ha(-1)), For each year, the g enotype x row-spacing interaction was not significant. However, the co mbined analysis (1992, 1993) indicated that the P > F for the genotype x row-spacing interaction was 0.12. This was due to a trend for the c ultivars to respond to 76-cm rows (9% increase) whereas the okra-leaf types did not respond to 76-cm rows, Despite genetic differences in mo rphology and canopy architecture, genotype x row-spacing interactions may not be important when comparing 76- and 102-cm rows in some U.S. M id-South environments.